Stacking 2920 Switches

[dmccar12]

Hi All,

I prevously have worked with 2910al Switches and stacked them, so that they were all accessible by one IP Address.

I have never, with the 2910al Switches, purchased a stacking module, but, was always able to stack them together in one big stack or a smaller stack based on location, depending on the situation.

However, with the end of sale announced for 2910s, I was recently sent 18 2920s, and I want to stack them together so that all are accessible via one IP address, however, for the life of me, I can not get them stacked.  Some reading on the process showed me that the Stacking Module is necessary for stacking now, and that only allows 4 Switches per stack.

Is this true?  I am hoping I am just missing something as the cost of the Stack Unit is very great, and if I need this Stacking Unit Module, I will be pretty upset.

Hopefully, like I said above, I am just missing something.  But is it possible to stack 2920s, without the Stacking Module?

Thank you,

Dave

[Pete W]

Dave,

The issue here is HP's overloading of the word "stacking".

Previously, HP had a stacking technology that simply permitted management of multiple switches through a single IP address. The only benefit of this approach being IP address conservation, and it was not particularly widely deployed (in my experience).

The industry however has a different opinion of what a "stacking" technology is. Commonly a stackable switch solution:

• Provides single IP address management
• Uses a single configuration file for whole stack
• Acts like a single physical switch in relation to routing and switching operations (spanning-tree/routing).

A common acid-test of whether a switch stack is a "real" stack is whether or not you can form a cross-switch LACP aggregation.

Anyway, the 2920 does indeed form a true stack, and to do so requires the stacking-kit to be installed on both switches. The "Advanced Traffic Management Guide" document (page 7-1) states the following:

• Note that this feature is different from the stacking feature that is implemented on some other HP Networking switches. The other feature is implemented via the front-panel networking cables, and it does not have the highbandwidth and redundancy features of the HP 2920 and 3800 stacking.
• The stacking feature for the HP 2920 switches allows you to connect up to four switches and have them act as a single high-bandwidth switch for both data and management.

So having looked at the docs - it does not look like the legacy HP stacking is available on the 2920.

Hope this helps...

Regards,

Pete